Cryptocurrency is a type of digital or virtual currency that uses cryptography for security, making it difficult to counterfeit or double-spend. Unlike traditional money issued by governments, cryptocurrencies operate on decentralized networks based on blockchain technology, which records all transactions transparently and immutably. Popular examples include Bitcoin and Ethereum. Cryptocurrencies can be used for legal purchases, investments, and transferring funds globally. However, their relative anonymity and lack of centralized oversight have also made them attractive for illicit activities, such as money laundering and cybercrime.